THRASHING AROUND in the grip of the budget, the Reagan administration is reaching toward a couple of wildly misguided remedies. With the support of the Republican congressional leadership, the White House is talking about impoundment legislation. Impoundment means letting the president decide which appropriations to spend, and which not to spend. It's the line-item veto of appropriations that many presidents have sought. But Congress has refused it, recognizing it to be a massive transfer to the presidency of the constitutional power--and responsibility--to set spending policy.

For Sen. Howard Baker and Rep. Robert Michel to encourage this idea is an astonishing abdication. It amounts to saying that the congressional Republicans want further cuts in the budget--but not by them. They don't want their fingerprints to be found anywhere around the scene of the next round of cutting. They want the deed done far from them, over at the White House, behind closed curtains.

This dodge not merely would be craven on the part of Congress, but would also mean an important shift in the balance between the two branches of government. To see the implications, you have only to recall recent history. President Nixon claimed the authority to impound, and used it vigorously and illegally in the early 1970s, a period in which the presidency's assertions of its rights and powers had swollen dangerously out of measure. The courts told Mr. Nixon to stop it, and Congress wrote, in the Budget Reform Act of 1974, an orderly and reasonable procedure to rescind unneeded appropriations. That rescission process has been used effectively this year to cancel spending that Congress now considers excessive. But the procedure requires congressional votes, and that is what the Republican leaders are evidently trying to avoid.

Meanwhile a different sort of bad idea has emerged at the Pentagon, where officials are talking of a "sliding scale" of defense appropriations. They want to slide some of the increment in spending out past 1984 --the year when the president has pledged to balance the budget. Unlike impoundment, this one has no deep constitutional meaning. It's a mere fiscal fakery.

Balancing the budget briefly during a political campaign will be meaningless, if everyone sees that a huge accumulation of spending commitments will roll into the budget immediately after the election. Abroad, this country's NATO allies--not to mention the Soviets--would assume that the postponement meant a wavering of intentions here. But at home, the financial markets would foresee a ballooning of deficits beginning in 1985 and would discount any temporary gestures toward restraint. The administration's budget dilemma is genuine, and it is not going to be resolved by resorting to creative accounting.

The administration's dilemma is the result of a tax cut that was too large. This has left the country with revenues inadequate to support both the defense effort that Mr. Reagan considers essential, and the domestic programs that Congress--even a conservative Congress with a Republican Senate-- considers essential. There is only one genuine solution, and that is to raise taxes again. As long as Mr. Reagan refuses to consider that possibility, the budget problem remains insoluable.